vertebral arteries and internal carotid arteries give rise to an anastomosis that supplies the brain

Internal Carotid Arteries

 enter at the carotid canal in the temporal bone, makes a 180o turn in the cavernous sinus, upon leaving the cavernous sinus gives off the ophthalmic artery (to the orbit) and then contributes to the circle

Vertebral Arteries

 enter through foramen magnum, join in midline to form the basilar artery and contribute to the circle

the vertebral arteries supply ~25% of the brains blood, the internal carotids supply ~75% of the brains blood

nine arteries of the circle of Willis

(not counting the Basilar artery) listed anterior to posterior:

anterior communicating artery

right and left anterior cerebral  the anterior cerebral arteries supply most of the medial and superior surfaces and the frontal lobe

right and left internal carotid  the internal carotids give off the middle cerebral artery after contributing to the circle

right and left posterior communicating

right and left posterior cerebral

aneurysms

occur at branch points, often where posterior communicating artery comes off internal carotid artery; also at basilar artery

Emerge from the brain stem at the caudal border of pons, lateral to the superior end of the olive.

Both roots enter the internal acoustic meatus form the geniculate ganglion then exit skull at stylomastoid foramen.

Branches of the facial nerve

Greater petrosal nerve

: branches off at the geniculate ganglion to exit via the hiatus of the facial canal

contains taste and parasympathetic fibers,

merges with the deep petrosal nerve (sympathetic fibers) in the pterygoid canal to form the Vidian nerve

then enters the pterygopalintine ganglion, which sends the sympathetic and postynaptic parasympathetic fibers to the lacrimal gland and the mucosa of the palate, nasopharnyx, and nasal cavity via connections to V2and then branches of its Zygomatic branch.

Chorda tympani nerve

branches in the facial canal and exits the skull via the petrotympanic fissure

Joins the lingual nerve (branch of V3) which runs to anterior 2/3 of tongue and provides taste sensation (CN V).

Parasympathetics in the lingual nerve synapse in the submandibular ganglion then supply the submandibular and sublingual glands

Stapedius nerve

arises in the facial canal and is motor to the muscle on the stapes.

Suprahiod motor branches

exits stylomastoid foramen then supplies the stylohiod m, posterior belly of the digastric and the 5 Facial branches which arise within the parotid gland  temporal, zygomatic, buccal, mandibular, cervical

Nuclei of the facial Nerve

:

Facial Motor nucleus

gives rise to the motor fibers and is located in the ventro lateral part of tegmental pons

Nucleus Solitarius

(rostral portion) receives the afferent taste roots

Geniculate ganglion

contains the cell bodies of the for 1o sensory neurons; the pain, touch and thermal sensations from around the ear end in the descending trigeminal nucleus.

one small motor nerve for the muscles of mastication and three principal general sensory nerves from the head.

CN V1 (Opthmalic Nerve):

purely sensory from superficial and deep parts of superior region of the face.

passes anteriorly in the lateral wall of the cavernous sinuses, inferior to the trochlear nerve.

All 3 of its branches pass enter the orbit through the superior orbital fissure.

Frontal nerve

: largest branch travels anteriorly to the supra orbital area giving off the supra orbital branch that provides sensation from the upper eyelid and scalp; and the supratrochlear nerve that also provides sensory from the upper eyelid and forehead.

Naso cilliary nerve

: enters orbit through the central tendinous ring on its way to innervating the medial wall.

Lacrimal nerve

: smallest of the main branches; enters via the superior orbital fissure on its way to lacrimal gland and nearby structures.

CN V2 (Maxillary Nerve)

: purely sensory; arises from the Trigeminal ganglion running anteriorly in the inferior cavernous sinus, inferior to the Opthmalic nerve.